1. Field of the Invention
The present invention relates to power dividers and power combiners in telecommunications, and in particular relates to an M-way coupler having one input port and M output ports or having M input ports and one output port.
2. Description of the Related Art
In a phased array, the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions. The elements of a phased array are connected by power dividers and power combiners. Power dividers and power combiners are used in the field of radio technology to couple a defined amount of electromagnetic power in a transmission line to another port where it can be used in another circuit. Hereinafter, “M-way coupler” is a general term for the power dividers and power combiners, where M represents an integer, and an M-way coupler may have one input port and M output ports (as a power divider) or have M input ports and one output port (as a power combiner). An essential feature of the M-way couplers is that they only couple power flowing in one direction. Power entering the output port is not coupled. To reduce the amount of M-way couplers required to build a phased array, the current trend is to increase the number M.
However, a large M may result in non-identical circuits in the coupling paths of the M-way coupler and may increase the complexity of connecting the M-way coupler to other function blocks. An M-way coupler with a symmetric layout (e.g. having identical circuit design for all coupling paths) and having the M input/output ports widely spaced apart from each other, thereby simplifying the routing lines between the M-way coupler and other function blocks, is called for.